For good preventive maintenance, you should flush your system about once a year. I use prestone flush.
always use DEMINERALIZED water. a little water wetter never hurts. the water level sensor works off a ground, so if it's bad it'll just keep buzzing. Using jumper cables to ground it, will keep the buzzing at bay. The replacement is less than $10.


If you replace the thermostat use nothing but the stock Mazda one. Others seem to crap out early.

 

and brown is never a good color for coolant in ANY car.

 

iliketoeatricers you are the ****!!!!! following your advice i drove the car around a bit, pulled over released the air pressure from the radiator and repeated 3 times. topped off the radiator before the 3rd drive and no buzzer after that! thanks again man you rock!

 

Glad to hear that you solved the problem yourself. Congratulations.